This invention relates to dielectric materials and in particular, but not exclusively, high dielectric constant dielectric materials for capacitors and other devices such as sensors.
Dielectric materials are used in various electrical components for various purposes. In the case of capacitors dielectric materials may be employed as the dielectric between metallic electrodes, or in the case of sensors, dielectric materials may be employed to provide substrates on which sensing films are arranged. Conventionally the dielectric materials may be powders which are mixed with binder and solvents, formed to a required shape and then sintered in order to reduce porosity.
The dielectric material most commonly employed is barium titanate which has a dielectric constant of the order of 1500. Very much higher dielectric constant values are, however, provided by bulk dielectric materials such as PbFe.sub.2/3 W.sub.1/3 O.sub.3, PbFe.sub.1/2 Nb.sub.1/2 O.sub.3 and PbZn.sub.1/3 Nb.sub.2/3 O.sub.3. With suitable choice of materials it has already been demonstrated that multilayer ceramic capacitors can be produced in which the ceramic dielectric constant is 20,000 or more. These known multilayer ceramic capacitors were, however, manufactured using the conventional process of mixing powders with binders and solvents and forming them to a required shape, by, for example, pressing. After screen printing of electrodes thereon and the assembly of stacks of electrode-carrying ceramic bodies, the stacks must be fired in order to sinter the ceramic to reduce porosity.